This invention relates to dialkyl perfluoro-.omega.-fluoroformyl esters and to monomers and copolymers made therefrom. Following are descriptions of several background developments which provide a context in which to appreciate the present invention.
Krespan, in South African Pat. No. 77/7158, disclosed O.dbd.C(CF.sub.2 CO.sub.2 CH.sub.3).sub.2, perfluoroalkyl ether dicarboxylates prepared therefrom and perfluorinated copolymers from said dicarboxylates. The perfluoroallyl ether dicarboxylates are neither homologs nor analogs of the perfluorovinyl ether dicarboxylates described herein.
Selman, in U.S. Pat. No. 3,274,239, disclosed fluoroketones of the formula, XR.sub.F C(O)R'.sub.F X', where X and X' are H or halogen and R.sub.F and R'.sub.F are perfluoroalkylene of 1 to 8 carbon atoms; hexafluoropropene oxide (HFPO) adducts thereof, (XR.sub.F)(X'R'.sub.F)CFO(CF(CF.sub.3)CF.sub.2 O).sub.n CF(CF.sub.3)COF, where n is 0 to 20; and vinyl ethers formed from said adducts.
England, in U.S. Pat. No. 4,131,740, disclosed the reaction of HFPO with a compound of the formula FOC--CF.sub.2 --CO.sub.2 R in the presence of fluoride ion as catalyst and an inert liquid diluent (preferably an organic liquid) in which the selected fluoride is at least 0.001% soluble, to form alkyl perfluoro-.omega.-fluoroformyl esters, RO.sub.2 CCF.sub.2 (CF.sub.2 O(CF.sub.3)CF).sub.n COF, where n is 0 to 6. Also disclosed are vinyl ethers formed from the esters, and perfluorinated copolymers of the vinyl ethers.
England, in U.S. Pat. No. 4,138,426, disclosed perfluorovinyl ethers, YCF.sub.2 (CF.sub.2 O(CF.sub.3)CF).sub.p CF.sub.2 OCF.dbd.CF.sub.2, wherein Y is --CO.sub.2 R, --CO.sub.2 H, --CO.sub.2 M, or --CN; R is 1 to 6 carbons; M is alkali metal, ammonium or quaternary ammonium; and p is 1 to 5.
Breazeale, in U.S. Application Ser. No. 083,751, filed Oct. 22, 1979, disclosed vulcanizable copolymers of tetrafluoroethylene, perfluoromethyl perfluorovinyl ether and a cure site monomer consisting of a cyano-substituted perfluorovinyl ether of the formula, CF.sub.2 .dbd.CF[OCF.sub.2 CF(CF.sub.3 ----.sub.x O(CF.sub.2).sub.n CN, where n is 1 to 4 and x is 1 or 2.